When the control voltage or the drive power supply for the switching devices fails or is switched off in electrical switchgear assemblies, in the event of a malfunction or during planned maintenance work, then aids, such as hand cranks, are provided which allow the switching devices, which may possibly remain in an intermediate position, to be moved to a desired limit position. On the other hand, apparatuses are also known from switchgear technology for blocking the rotation of a shaft of an electrical drive for a moving contact of a switching device, which apparatuses prevent operation of switching devices at an unacceptable time, or by unauthorized personnel. These apparatuses are used for personal protection of the personnel working in the switchgear assembly, and also for operational reliability of the respective switchgear assembly.
However, it may also be necessary for example, to switch on grounding devices by hand so that the fitter can safely carry out repairs or maintenance work in the switchgear assembly. The hand cranks which are required for this purpose are connected in an interlocking manner to the drive shaft of the relevant switching device. In order to prevent unauthorized manual operation of these drives, the access to this drive shaft is prevent by means of safety covers. When manual actions are intended to be carried out, then an appropriate specialist person is employed by a control center to carry out these switching operations. Only this person has the necessary special tool in order to remove these safety covers. It is also possible to interrupt the electrical control circuit for the relevant drive motor by means of limit switches which are operated by the hand crank, in order to prevent the possibility of the drive motor being electrically initiated, for as long as it is being moved manually.
DE 197 12 346 discloses an electromechanical apparatus for blocking the rotation of a shaft of an electrical drive for a moving contact in a switching device. DE 41 10 982 discloses a locking apparatus for blocking or releasing a shaft end, onto which an operating lever for manual rotation operation can be pushed.
However, there are various problems which are not solved by the known apparatuses, for example relating to safe and reliable operation and the capability for quick and simple manual access, particularly in the event of failure of the electrical supply.